Seismic Focus : In seismology, the point within the earth that is the center of an earthquake. It is the initial rupture point of an earthquake, where strain energy is transformed into elastic wave energy. See epicenter
Intergovernmental Oceanographic Commission IOC technical series 37, Tsunami Glossary (A glossary of terms and acronyms used in the tsunami literature - English), , United Nations Educational, Scientific and Cultural Organization UNESCO, Paris, France 1991. http://unesdoc.unesco.org/images/0008/000885/08853 8eb.pdf, (ND/ Tsunami Sci - Brit) {590}